Cut the aubergine into cubes about 2cm. Toss well into 40ml olive oil. Place in a roasting dish spreading well and roast at 180/Gas mark 4 for about 20 minutes until soft and starting to brown.
Heat the remaining oil and fry the onion and celery until soft.
Add the tomatoes, chilli, salt and pepper and simmer for 10 minutes.
Add the capers, olives, vinegar, sugar and chocolate. Stir well and simmer for 10 minutes.
Stir in the aubergines until full coated with the sauce. Remove from the heat.
Leave to stand in the pan for at least 30 minutes to allow the flavours to blend.
Serve sprinkled with pine nuts and basil or parsley.